TW1 got away with it because of the amnesia thing, TW2 tells the story of Geralt getting his memory back, but you're left in the uncomfortable position of Geralt starting to remember about key characters (Yennifer, Ciri etc.) while it's the first time as a player you will have heard about them. Several in-game consequences are then dependant on these previous events (as described in the books), such as Triss' reactions and decisions, but if you haven't read the books then these seem to come out of nowhere.

And that is politics? It looks like the smaller picture, that is the character's direct environment.
Not the bigger picture, what is going on beyond the direct Witcher environment.
And there is always a first time. There are players who have not understood who Yennefer and Ciri were after playing the two games?If so, why?
Of Rivia has not yet recovered his memory and the player accompanies the character in this rediscovery of himself.

And both characters (Yennefer and Ciri) were introduced in TW1 by an innkeeper (cant remember which), the guy that tells the story of TW as it was a fairy tale. This tale recounts the most relevant points concerning the three characters.
People who played the first episode did not start blank on this one, going into TW2.
Players who did not, yes.

The background required isn't at all addressed in TW1. The prologue of TW1 addresses the pertinent points to the gameplay of TW2, ie, Geralt's memory loss and what Witchers are etc. but has next to nothing about the characters important in Geralt's life that are relevant for the main story reveals in TW2.

Again the smaller picture. Nothing about how TW1 installs the overarching story in which Of Rivia is going to evolve across the two episodes of the series.